The usefulness of the mouse hippocampal slice preparation and the study of the role of potassium in the generation of ictal activity was the subject of this research. The methods included studying the effects of various extracellular potassium (K+) concentrations on spontaneous or pentylenetetrazol (PTZ) induced discharges both in the presence and absence of anticonvulsant agents. Standard techniques were used to obtain extracellular recordings in the CA3 region of hippocampal slices from NIH general purpose mice. The K+ concentration in the medium was adjusted with potassium chloride, and the effects of these manipulations were noted. It was found that no spontaneous bursts occurred at low K+ (3.25 mM), but spontaneous bursts occurred at low K+ (3.25 mM), but spontaneous discharges were observed in a majority of the slices at higher K+ (9.25 mM). PTZ-induced discharges occurred in slices at concentrations ranging from 100 ug/ml to 200 ug/ml and were found to be positively correlated to increasing K+ concentration. This PTZ-induced activity was reversible. These observations substantiate the putative role of potassium in the generation of ictal episodes and the modulation of hippocampal neuronal excitability. Preliminary investigations using anticonvulsant agents show that clonazepam abolished the bursting elicited with PTZ whereas phenytoin did not. These results are similar to those obtained using the in vivo pentylenetetrazol subcutaneous threshold test in mice.